1. Field of the Invention
The present invention relates to radio equipment performing transmission and reception corresponding to a plurality of sectors. In particular, the present invention is preferably applied to realize a sector-free radio base station, in a cellular system employing OFDM and OFDMA. Here, sector-free signifies a state in which a PHY unit for generating a signal corresponding to each subcarrier can be shared among RF units corresponding to the plurality of sectors.
2. Description of the Related Art
There has been adopted a cellular system performing transmission and reception in one radio base station, with different frequencies assigned to a plurality of sector antennas.
For example, in the Domestic Republication of PCT Publication WO98/13956 (hereafter referred to as Patent document 1), there is shown a configuration including transmitter/receivers provided on each sector basis, baseband processors on each sector basis, and a switch for selecting the connection between the baseband processors and the transmitter/receivers.
Also, in the official gazette of the Japanese Unexamined Patent Publication No. Hei-10-164637 (hereafter referred to as Patent document 2), in a CDMA cellular mobile communication system, there is a description of dividing the service area of one cell base station into a plurality of sectors. Also, there is shown switchover control according to the movement of a mobile terminal, so as to select among transmission/reception antennas each serving an area corresponding to each of the plurality of sectors.
Further, in the official gazette of the Japanese Unexamined Patent Publication No. 2002-345013 (hereafter referred to as Patent document 3), there is shown sector transmission and reception, in which a cell covered by a radio base station is divided into a plurality of sectors respectively having an identical area. The above sector transmission/reception system has a feature that a cell includes a first area constituted of a predetermined number of sectors, and a second area being disposed inside the first area and constituted of sectors smaller in number than the above predetermined number, and further, there is disclosed a sector division method reducing processing amount for handover control.
Now, for communication systems in recent years represented by WiMAX (World Interoperability for Microwave Access) communication, large capacity and high speed have been required. As communication methods to realize such requirements, there are adopted OFDM (Orthogonal Frequency Division Multiplexing) and OFDMA (Orthogonal Frequency Division Multiple Access), having a feature of performing Fourier transform and inverse Fourier transform for transforming between a signal in the frequency domain and a signal in the time domain.
In the inventions described in the above Patent documents 1 to 3, although sector transmission/reception is disclosed, no guideline has been shown about the relation to be applied between distribution to sectors and the transformation processing such as Fourier transform and inverse Fourier transform.